bug#23144: shrinking windows with gtk 3.20

[martin rudalics]

> If it's a serious bug, maybe; it depends on the scope of the change and the
> number of users it affects. 25.1 _will_ ship with some bugs, we can't avoid
> that; so at this point we're trying as much as possible only to improve the
> stability of our pretests.

It's not about the severity of the bug; it's merely about how to react.

I think we have two possibilites to deal with this issue: Ignore it or
implement a fix.  If we ignore it, we might run into difficulties later
when gtk developers eventually decide to apply the change in question or
we find a case where our code does not DTRT anyway.  As Eli already
mentioned, after Jan's departure nobody here is in grade to maintain the
gtk interface reliably.

If we try to fix it, we could possibly rely on Matthias to give us clues
on how to proceed and what to do if the fix causes problems.  If the fix
goes into master, there are chances that any such problems will pass by
unnoticed for some time since currently most people here seem to use the
release version.

martin